The research team from the University of East Anglia looked at 14 years worth of data from a study of 69,622 women who reported on their food consumption every four years.

It was found that those who ate foods containing a specific sub-group of flavanoids, called flavanones - found in oranges and grapefruits - were at lower risk of a stroke than those who consumed other sources of flavonoids.

"Studies have shown higher fruit, vegetable and specifically vitamin C intake is associated with reduced stroke risk," said Dr Aedin Cassidy, professor of nutrition at UEA's Norwich Medical School and author of the study.

"Flavonoids are thought to provide some of that protection through several mechanisms, including improved blood vessel function and an anti-inflammatory effect."